The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.
Browsers are powerful computer program applications that may execute instructions, received from a web server, to generate complex user interfaces that are presented to a user through one or more devices, such as a display monitor or speakers. Perpetrators of fraud or theft (“fraudsters”) may inject malicious instructions, which when executed by a browser, may cause, among other things, sensitive data to be sent to an unknown party, the client computer to be used for a cyber-attack, or malware to be installed on the client computer.
Browsers prevent some malware from being installed on a client computer by limiting functionality. For example, a browser, executing on a client computer, may restrict a JavaScript run-time environment from accessing files stored on the client computer. However, fraudsters regularly find new ways to embed malicious software through a browser. For example, a fraudster may embed a key-logger program into an image file. After a browser downloads an image file referenced in a web page, the browser may store the image on the client computer. Opening the image file may cause executing the key-logger on the client computer. The key-logger may record data indicating each keystroke a user makes regardless of which program the user is currently using on the computer. The key-logger can send the recorded data back to the fraudster.